Apparatus for aligning the shadow mask with respect to the face panel of a cathode ray tube

ABSTRACT

Improved apparatus is provided for aligning the shadow mask with respect to the face panel of a cathode ray tube of the shadow mask type. Basically, it comprises first means for supporting the face panel in a first position, second means for supporting frame means for the shadow mask in a second position spaced apart from the face panel, and third means for supporting the shadow mask for movement relative to the frame means and the face panel.

United States Patent Smith et al. [451 Apr. 4, 1972 [54] APPARATUS FOR ALIGNING THE [56] References Cited SHADOW MASK WITH RESPECT TO UNITED STATES PATENTS THE FACE PANEL OF A CA HODE 3,284,884 11/1966 Prazak ..29/200 J RAY TUBE 3,482,286 12/1969 Fasset et al. ..29/464 x Carl L. Smith, Auburn; William H. Nicklas, N. Syracuse, both of NY.

Assignee: General Electric Company Filed: Mar. 19, 1970 Appl. No.: 20,898

Inventors:

U.S. Cl. ..29/203 J, 29/203 P, 29/464 Int. Cl. ..B23p 19/00, H05k 13/00, B23g 3/00 Field of Search ..29/203 J, 203 P, 464

Primary Examiner-Thomas H. Eager Attorney-James E. Espe, Francis H. Boos, Jr., Frank L. Neuhauser, Oscar B. Waddell and Joseph B. Forman [5 7] ABSTRACT Improved apparatus is provided for aligning the shadow mask with respect to the face panel of a cathode ray tube of the shadow mask type. Basically, it comprises first means for supporting the face panel in a first position, second means for supporting frame means for the shadow mask in a second position spaced apart from the face panel, and third means for support ing the shadow mask for movement relative to the frame means and the face panel.

7 Claims, 4 Drawing Figures PATENTEDAPR 41922 3,653,112

SHEET 1 OF 2 INVENTORS mm. L. SMITH &W\L.LIA H. NICKLAS BY 1 THEII ATTORNEY PATENTEUAPR 4 m2 3,653,112

SHEET 2 BF 2 INVENTORS F '56 4 CARL 1.. SMlTH WILLJAM H. NKZKLAS Q a TH IR ATTORNEY APPARATUS FOR ALIGNING THE SHADOW MASK WITH RESPECT TO THE FACE PANEL OF A CATHODE RAY TUBE BACKGROUND OF THE INVENTION This invention relates to color cathode ray tubes of the shadow mask type and, more particularly, to improved apparatus for aligning the shadow mask with respect to the face panel of such a tube.

One of the most complex devices mass-produced for the consumer market is the color cathode ray tube of the shadow mask type that is widely used as the picture tube in a color television receiver.

The envelope of a color cathode ray tube of the shadow mask type comprises a funnel part having a neck portion in which a multi-beam electron gun structure is mounted and a face panel part which is sealed to the large end of the funnel at a certain stage in the manufacture of the tube. The face panel comprises a transparent face plate, on the inner surface of which a mosaic of three different color emitting phosphors is laid down, and has a peripheral wall or skirt portion on which the shadow mask is mounted. The face panel has a curved inner surface and the shadow mask has a similar, but not identical, surface positioned within a predetermined spacing, called Q by the industry, in the general order of one-half inch from the face panel, measured normal to the inner surface of the face panel. In operation of the tube, electrons from each of the three beams pass through the apertures in the shadow mask and strike the phosphor dots of only one of the three colors. The phosphor dots for each color are usually formed on the face panel by a photographic method using the shadow mask as a stencil. Thus, the shadow mask must be detachably mounted on the face panel so that it can be easily removed and replaced in exactly the same position every time. The mask is frequently mounted by means of plural strap-like members or leaf springs, each welded at one end to the mask or its frame means and having an aperture at the other end for engaging an inwardlyextending fixed stud provided on the skirt portion of the face panel.

Usually, the mask is supported around its periphery by frame means, with the mask periphery being bent relative to its major plane to provide it with a skirt portion that is telescoped over the mask frame means and welded thereto to form a mask-frame assembly.

Heretofore, the mask and its frame means have been first welded together to form the mask-frame assembly, which is subsequently aligned relative to the face panel, and various apparatus have been provided in the past for aligning this mask-frame assembly with respect to the face panel. U.S. Pat. No. 3,482,286 and a recent publication by Mr. Joseph A. Ritts of Moore Products Company illustrate typical versions of such prior-art apparatus. Some of these prior-art machines also include means for welding the spring mounting clips to the periphery of the mask-frame assembly after completion of the critical alignment or Q"-spacing step. All of these prior-art machines have an inherent problem in obtaining truly accurate alignment of the shadow mask with respect to the face panel in that they take a pre-joined mask-frame assembly, wherein the mask may already be fixed misaligned with respect to its frame means, and then proceed to align or space this mask-frame assembly with respect to the face panel.

SUMMARY OF THE INVENTION It has been found that the aforedescribed problem can be overcome by the improved apparatus that is provided by the present invention. Basically, it comprises first means for supporting the face panel in a first position, second means for supporting the frame means for the shadow mask in a second position spaced apart from the face panel, and third means for supporting the shadow mask for movement relative to the frame means and the face panel.

Thus, with this improved apparatus of the present invention, the shadow mask is not fastened to its frame means until the critical-step of aligning or Q"-spacing of the mask with respect to the face panel is performed. And, in addition, use of the improved apparatus of the present invention permits welding of the mounting clips to the mask frame means prior to performing the critical step of aligning or Q"-spacing the mask with respect to the face panel. Hence, no further welding (and with it unwanted thermal distortion) need be performed on the mask-frame assembly following completion of this most critical alignment.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is illustrated in the accompanying drawings, wherein:

FIG. 1 is a fragmentary sectional view showing the location of the shadow mask in the envelope of a typical color cathode ray tube;

FIG. 2 is a somewhat schematic, fragmentary, partly sectioned elevational view of a presently preferred embodiment of the present invention, showing the apparatus in a first condition of its operation;

FIG. 3 is a top plan view of the apparatus shown in FIG. 2; and

FIG. 4 is a view generally similar to FIG. 2, but showing the apparatus in a second condition of its operation.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, and, more particularly, to FIG. 1 thereof, there is illustrated a portion of the envelope 10 of a typical color cathode ray tube 11 of the shadow mask type. The envelope 10 of the tube 11 comprises a funnel part 12 having a neck portion (not shown) in which a multi-beam (usually three-beam) electron gun structure (not shown) is mounted and a face panel part 14 which is sealed to the large end of the funnel 12 at a certain stage in the manufacture of the tube 11. The face panel 14 comprises a transparent face plate 15, usually made of glass, on the inner surface of which a mosaic 16 of three different color emitting phosphors is laid down, and has a peripheral wall or skirt portion 17 on which a foraminous electrode member, commonly known as the shadow mask 18 is mounted. The face panel 14 has a curved inner surface and the shadow mask 18 has a similar, but not identical, surface positioned within a predetermined spacing, called Q by the industry and in the general order of one-half inch from the face panel, measured normal to the inner surface of the face panel. In operation of the tube 11, electrons 19 from each of the beams pass through one of the many apertures 20 provided in the shadow mask 18 and strike the phosphor dots of only one of the multiple colors forming the mosaic 16. The phosphor dots 13 for each color of the mosaic 16 are usually formed on the face panel plate 15 by a photographic method using the shadow mask 18 as a stencil. Hence, the shadow mask 18 must be detachably mounted on the face panel 14 so that it can be easily removed and replaced in exactly the same position every time. The mask 18 is frequently mounted by means of plural strap-like members or leaf springs 21, each welded at one end to the mask 18 or its frame means 22 (which will be described in detail below) and having an aperture 23 at its other end for engaging an inwardly extending fixed stud 24 provided on the skirt portion 17 of the face panel 14.

Usually the shadow mask electrode 18 is supported around its periphery by the frame means 22, with the mask periphery being bent relative to its major plane to provide it with a mask skirt portion 25 that is telescoped over the mask frame means 22 and welded thereto to form a mask-frame assembly 26.

Heretofore, as noted above, the shadow mask 18 and its frame means 22 have been first welded together to form the mask-frame assembly 26 which was then aligned relative to the face panel 14, and various apparatus (not shown) have been provided in the past for aligning this pre-joined maskframe assembly 26 with respect to the face panel 14. And, some of these prior-art machines also included means (not shown) for welding the spring mounting clips 21 to the periphery of the pre-joined mask-frame assembly 26 after completion of the critical alignment or -spacing step. Thus, all of these prior-art machines have had an inherent problem in obtaining truly accurate alignment of the shadow mask with respect to the face panel in that they take a prejoined mask-frame assembly, wherein the mask 18 may already be fixed misaligned with respect to its frame means 22, and then proceed to align or Q-space this mask-frame assembly 26 with respect to the face panel 14.

In accordance with the present invention, it has been found that the aforedescribed problem can be overcome by the improved apparatus that is provided by the present invention, a presently preferred form of which is illustrated in FIGS. 2-4 of the accompanying drawings. As illustrated, this improved apparatus or machine 30 basically comprises first support means 31 for supporting the face panel 14 in a first position (FIG. 4), second support means 32 for supporting the frame means 22 for the shadow mask 18 in a second position (FIG. 4) spaced apart from the face panel 14, and third support means 33 for supporting the shadow mask 18 for movement relative to both its frame means 22 and the face panel 14.

As shown in greater detail in FIGS. 2-4, the improved apparatus or machine 30 of the present invention comprises a hollow frame-like member or table which includes a lower portion 41 that is supported by rollers 42 for rotary movement in a generally horizontal plane with respect to a fixed base plate 43. The general arrangement of the rotatable table 40 with respect to the fixed base plate 43 is analagous to and commonly referred to as a Lazy Susan.

The table 40 supports the remainder of the mechanism for the machine or apparatus 30 of the present invention, including the aforedescribed first, second and third support means 31, 32 and 33. As illustrated, both the first and second of these support means 31 and 32 are provided by a set of three Z- shaped arms 44, each of which is pivotally mounted on an axle 45 that is generally horizontally arranged in an opening 46 provided in a plate 47 which forms the top of the rotatable table 40.

As shown in FIGS. 2-4, the lower end of each of these Z- shaped arms 44 comprises the first support means 31 and is provided with first engagement means in the form of a notch 48 which is constructed and arranged to be engageable with first connector means comprising one of the studs 24 that are provided on the skirt portion 17 of the face panel 14. And, the upper end of each of these Z-shaped arms 44 comprises the second support means 32 and is provided with second engagement means comprising a pseudo-stud 49 which is constructed and arranged to be engageable with second connector means comprising the aperture 23 that is provided in one of the ends of the strap-like members or leaf springs 21 which are welded to the frame means 22 for the shadow mask 18.

As shown in FIGS. 2-4, each of the Z-shaped arms 44 is yieldably urged or biased towards movement in a first direction (clockwise as seen in FIGS. 2 and 4) about its axle 45 by yieldable means, such as a coil spring 50, that is connected between one side of the arm 44 and a bracket 51 that is fastened to and extends downwardly from the top plate 47 of the table 40. However, the yieldable urging of the spring can be overcome and the arm 44 can be moved in an opposite direction about its axle 45 by energization of a fluid motor, such as an air cylinder 52, that is connected between the opposite side of the arm 44 and another bracket 53 that is fastened to and extends downwardly from the table top plate 47. Guide means, comprising a pair of parallel blocks 54 and 55, are provided atop the top plate 47 of the table 40 on opposite sides of the opening 46 for guiding the movement of each of the Z-shaped arms about its axle 45.

As further illustrated in FIGS. 2-4, the third support means 33 comprises a generally rectangular plate 56 which is imbedded with a plurality of electro-magnets 57 and is generally horizontally arranged over the top plate 47 of the table 40. The magnet-carrying plate 56 has a substantially flat lower surface and a concave upper surface that is generally similar in shape to the convex front face of the shadow mask 18. As best shown in FIGS. 2 and 3, the geometric center of the magnetcarrying plate 56 is generally aligned with the geometric center of the top plate 47 of the table 40, and gauge means, comprising a vertically arranged spacer rod 58 having its upper end connected to the geometric center of the magentcarrying plate 56 and its lower distal end extended downwardly through bearing means 59 provided at the geometric center of the top plate 47 of the table 40. As further illustrated in FIGS. 2-4, conveyor means are provided for conveying the face panel 14 into engagement with the first support means 31. In the form of the apparatus 30 shown, these conveyor means comprise an elevator including another generally rectangular plate 60 which has a generally flat lower surface connected to the piston rod 61 of another fluid motor or air cylinder 62 that is, in turn, generally vertically arranged upon and mounted to the top of the lower plate 41 of the rotatable table 40. The elevator plate 60 has a concave upper surface which is adapted to receive and support the convex front surface of the face panel 14.

In use, the face panel 14 is loaded on the apparatus 30 with its convex face rested atop the concave surface of the elevator plate 60 of the conveyor means. Next, the two air cylinders 52 and 62 are energized and the face panel 14 is elevated and its studs 24 are respectively engaged with the notches 48 provided on the lower ends of the Z-shaped arms 44. Then, the shadow mask 18 is loosely telescoped over its frame means 22 to which the spring mounting clips 21 had been previously fixed by welding, with convex surface of the shadow mask 18 arranged centered on the concave upper surface of the magnet-carrying plate 56 and the apertures 23 of the mounting clips 21 connected over the pseudo-studs 49 provided on the upper ends of the Z-shaped arms 44. Now, the electro-magnets 57 carried by the third support means plate 56 are energized to pull the mask 18 against the plate 56 to move the shadow mask 18 vertically downward relative to both its frame means 22 and the face panel 14, with the extent of this downward movement, of course, being limited by the engagement of the lower end of the gauge means or spacer rod 58 with the concave inner surface of the face panel 14 and thus properly aligning or Q-spacing the shadow mask 18 with respect to the face panel 14. Finally, the skirt portion 25 of shadow mask 18 is now welded to its frame means 22, either by hand or with automatic equipment and the completed Q-d assembly can be removed from the apparatus 30 by deenergizing the electro-magnets 57 and the two air cylinders 52 and 62.

As will be evident from the foregoing description, certain aspects of the present invention are not limited to the particular details of construction of the form illustrated, and it is contemplated that various other modifications or applications will occur to those skilled in the art. For example, as shown in FIG. 3, but not in FIGS. 2 and 4, the gauge means might comprise a plurality of spacers, with additional spacer means 58 being vertically arranged adjacent the four corners of the plate 33 as shown in FIG. 3. Furthermore, the gauge means need not necessarily be connected to the third support means 33 nor be mechanical spacer means. Obviously, other forms of gauge means, such as pneumatic gauge means or the like might be substituted. It is therefore intended that the appended claims shall cover such applications or modifications as do not depart from the true spirit and scope of the present invention.

' We claim:

1. Improved apparatus for aligning the shadow mask with respect to the shadow mask frame means and the face panel of a cathode ray tube of the shadow mask type, comprising:

a. first support means for supporting the face panel in a first position;

b. second support means for supporting the shadow mask frame means in a second position spaced a predetermined distance from the face panel; and

means for conveying the face panel into engagement with said first support means.

6. The invention of claim 1, wherein the face panel is provided with first connector means and said first support means is provided with first engagement means engageable with said first connector means.

7. The invention of claim 6, wherein the frame means is provided with second connector means and said second support means is provided with second engagement means engageable with said second connector means.

IOK k 

1. Improved apparatus for aligning the shadow mask with respect to the shadow mask frame means and the face panel of a cathode ray tube of the shadow mask type, comprising: a. first support means for supporting the face panel in a first position; b. second support means for supporting the shadow mask frame means in a second position spaced a predetermined distance from the face panel; and c. third support means movable relative to said second support means for transporting the shadow mask to a location a predetermined distance from the face panel.
 2. The invention of claim 1, further including gauge means mountable between the face panel and said third support means.
 3. The invention of claim 2, wherein said gauge means is connected to said third support means.
 4. The invention of claim 2, wherein said gauge means comprises a plurality of gauge devices.
 5. The invention of claim 1, further including conveyor means for conveying the face panel into engagement with said first support means.
 6. The invention of claim 1, wherein the face panel is provided with first connector means and said first support means is provided with first engagement means engageable with said first connector means.
 7. The invention of claim 6, wherein the frame means is provided with second connector means and said second support means is provided with second engagement means engageable with said second connector means. 